Conventional fuel tanks often contain either an integral or separate reservoir for concentrating fuel within the tank to be supplied to an engine. The reservoir acts to confine fuel for pick-up by an in-tank fuel pump or fuel pick-up tube while the vehicle is undergoing a change of direction or speed. Plastic fuel tanks may be integrally molded with the reservoir shape in the bottom wall of the fuel tank. Metal fuel tanks generally use add-on reservoirs because the metal tank wall cannot be formed in the shape of the reservoir. These add-on type reservoirs may be either made of plastic or metal and secured to the fuel tank through mechanical means. The most common securing method includes forming a leg on the reservoir which lies along the fuel tank bottom. A metal strap is placed atop the leg and secured to the fuel tank bottom by welding, soldering, or brazing. The reservoir is held in place by one or more straps. If the straps become loose, the reservoir may shift out of position or rattle.
Securing the strap to the fuel tank bottom involves an expensive, time-consuming procedure. The interior wall of the fuel tank is generally treated to resist corrosion from the fuel. Welding or otherwise fastening the strap to the fuel tank may damage the coating. Additionally, the direct contact of the metal strap to the metal fuel tank wall may lead to a cathodic corrosion of either the strap or tank. It is desirable to provide a method of securing the reservoir within the fuel tank wall without using metal straps.
A number of fuel tanks teach the use of a plastic or rubber bladders within a metal fuel tank. U.S. Pat. No. 4,852,765 teaches a bladder for a fuel tank to separate the tank interior into a variable volume fuel space and air space. Bladders of this type are not used as fuel reservoirs and do not concentrate the remaining fuel within the tank for delivery to an engine. Bladders generally form fluid-tight enclosures to prevent fuel from contacting the fuel tank outer wall. Bladders generally reduce the overall volume of space available for containing fuel and increase the complexity of manufacturing a fuel tank assembly.
It is an object of the present invention to provide a reservoir secured within a fuel tank without the need of mechanical fasteners. It is another object of the invention to provide a reservoir which does not scratch, abrade, or damage the treated fuel tank surface. It is a further object of this invention to provide a low-cost method of manufacturing a fuel tank assembly.